Identification and characterization of a helicase-like protein encoded by a Thermus siphoviridae phage 4 gene

DNA helicases are essential motor proteins that unwind duplex DNA to yield the transient single-stranded DNA intermediates required for replication, recombination, and repair. As laboratory model strains of thermostable bacteria, the roles of Thermus have been studied and discussed extensively. In this study, one gene (ORF42) encoding a helicase-like protein of TSP4 (Thermus Siphoviridae phage 4) was identified and characterized. The results showed that ORF42 protein shared a higher homology to the DnaB helicases of Thermus bacteriophages P74-26 and P24-46. DNA helicase assay and atomic force microscopy (AFM) revealed that ORF42 protein was an Mg(2+)-dependent helicase with ATPase activity and involved in DNA unwinding. These evidences indicated that ORF42 protein, homologue of DnaB, probably acts as a helicase in TSP4. This study will not only contribute to explore the co-evolution of Thermus phages and their hosts but also shed a new light on the "arm-race" pattern between Thermus and its predator (TSP4), providing a basis for the theoretical investigations of new generation bacteriophage therapy.